Ideas for steel ball detection

[mechalloy]

How would you use a laser? They typically have a very focused beam, and most likely you would need a photo detector or am I missing something?

wmmullaney - on your link what do you mean about free pic samples?

 

[dknguyen]

How would you use a laser? They typically have a very focused beam, and most likely you would need a photo detector or am I missing something?

wmmullaney - on your link what do you mean about free pic samples?

Lasers are collimated by definition and don't need focusing. You either get a better made laser or a more powerful one, or both. Focusing only focuses the beam onto one point though (I think) and can't actually make a beam that has no divergence (doesn't spread).

Yes, you need a detector and use it like a trip-line.

 

[mechalloy]

That was my point about the collimated beam, in this case you have a small ball dropping down a very large diameter how would one make a laser detect over the whole cross sectional area of the diameter? With a laser as is you would only detect if the ball crossed the line of the laser so the ball may easily drop without hitting the laser line.

I think we have one set up I will try to see if the ball falls in a straight line or not.

 

[wmmullaney]

How would you use a laser? They typically have a very focused beam, and most likely you would need a photo detector or am I missing something?

wmmullaney - on your link what do you mean about free pic samples?

You need photo resistors, $2 at radio shack.

A Pic is a micro-controller, just like the avr, or arm. Are you familiar with any programming languages? Microchip gives you samples if you register, (free).


I could help you with the code if you want.

 

[arrie]

mechalloy, you will probably find the ball falling rather straight, you problem will most likely be the point of departure at the top.
Are you going to spin the ball across a horizontal axis at the drop point, then you apply a force in the liquid and will have some sideways movement, that could stuff up your whole experiment in any case?
I'm sure you used to get laser that wasn't just a straight line propagation, back in the day, but now I'm not sure, maybe someone will help us out. Or maybe it was another light spectrum. Diffused/ion something or other, damn this alzheimers-light.
Sorry can't help any more.

 

[Mikebits]

I would think that a laser light would have propogation issues going through glass and a liquid. Diffraction and diffusion would be my guess.

 

[arrie]

Yip you're right.
Laser can also be used very successfully with data transfer, yielding massive data transfer rates, years ago these systems have already passed 8Gb/sec.
That's serious rates man.
Only problem, mist and rain can really throw it off.
So I believe you might have a point.

Ahhhgggg, what the heck, lets just move into outer space, that will solve a lot of problems.
And to think of it, there you can fart as much as you like, and not feel guilty about greenhouse gasses etc.

 

[Mikebits]

And to think of it, there you can fart as much as you like, and not feel guilty about greenhouse gasses etc.

But there is no sound in space. Kinda takes the fun out of it...

 

[Torben]

But there is no sound in space. Kinda takes the fun out of it...

Oh, I don't know about that. Do lighters work in space?


Torben

 

[Mikebits]

Oh, I don't know about that. Do lighters work in space?
Torben

I think without pressure, the gas would just go poof like an elevator fart. Smell not included.

 

[Torben]

I think without pressure, the gas would just go poof like an elevator fart. Smell not included.

Which of course raises the question: should lighters be allowed in elevators?


Torben

 

[arrie]

Yes, but you can replace things like sound and smoking with something new, like..... uhhmmm....., like..... uhhmmm....., the fartalympics, that should be fun.

 

[wmmullaney]

What else would you use if lasers won't work and cameras are too expensive?

A little off subject I would say?

 

[jbeng]

That was my point about the collimated beam, in this case you have a small ball dropping down a very large diameter how would one make a laser detect over the whole cross sectional area of the diameter? With a laser as is you would only detect if the ball crossed the line of the laser so the ball may easily drop without hitting the laser line.

The divergence of a fan-shaped beam could be used to your advantage.

Use a laser with a line generator optic to get the fan shaped beam. Shine the fan through the tube with a linear array of phototransistor detectors on the opposite side to detect the shadow of the falling ball. The outputs of the sensors would be OR'd together to give a single pulse as the ball passes through the beam. Use two of these systems placed a known distance apart, triggering some sort of counting setup and you have what is known as a chronograph.

They're made commercially to time the speed of bullets, arrows, etc. Since the commercially made units are timing the speed of bullets, they're usually used outside and have a sensor which operates using ambient outdoor light instead of a laser.

Jeff